The federal and New South Wales governments will today announce they are spending nearly $3.5 billion on roads to support the construction of Sydney's second airport.

The money will flow over the next decade and the news has been welcomed by some nervous federal Liberal MPs in western Sydney who hope it will dampen community opposition to the Badgerys Creek project.

Last night many of the MPs had a phone hook-up with senior ministers to hear what an airport at Badgerys Creek might mean for them.

Unsurprisingly, many wanted to know if the airport would run around the clock. Some were worried about public support for the proposal, while others raised concerns about the direction of the runway.

The Liberal Member for MacArthur, Russell Matheson, has long fought against the Badgerys Creek project.

He would not talk about the details of the phone call, but says he is now determined to make the best of the current situation and secure as many jobs as he can for his electorate.

"My position hasn't changed in relation to Badgerys Creek. I want to see the concept, design, the airport, the runway alignment, the noise impacts, air quality," Mr Matheson said.

"At the end of the day I have to be pragmatic about it. The Government has made a decision to go ahead with Badgerys Creek. I've got to work out what the best outcomes for my community are."

Today Mr Matheson will join a handful of western Sydney Liberal MPs, Prime Minister Tony Abbott and Premier Barry O'Farrell for the announcement of a roads package which will support the construction of the Badgerys Creek project.

The package is worth just under $3.5 billion over the next decade, with $1 billion set aside over the budget forward estimates and some work likely to start within a year.

A large chunk of the money will go towards the Elizabeth Drive project, which is the road connecting the M7 Motorway to the Badgerys Creek site.

Two major arterial roads - the Bringelly and Northern roads - will also be upgraded, and about $200 million will be set aside for work on smaller, local streets.

The Commonwealth will contribute 80 per cent of the public funding. The NSW Government will make up the difference and will be left to foot the bill for any rail link.

The Coalition says there may not be enough airport traffic to justify a rail line in the early years of the airport's operation, but Labor's transport spokesman, Anthony Albanese, says that is rubbish.

"What we need is substantial investment, not just in roads but also in rail," Mr Albanese said.

What it could mean for Sydney's west

During construction, 1,529 jobs could be created over seven years

By 2050 the airport could create between $11.6bn and $15.2bn additional economic activity

Once operating fully, the airport would generate between 16,252 and 20,013 jobs

The airport could create 35,216 to 46,285 full-time equivalent jobs by 2050 directly or indirectly